Conditioning Transpetro's Gas Pipeline Network to the Baía De Guanabara Lng Terminal New Regasification Profile

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Proceedings of the 2014 10th International Pipeline Conference IPC2014 September 29 - October 3, 2014, Calgary, Alberta, Canada

IPC2014-33392

CONDITIONING TRANSPETRO'S GAS PIPELINE NETWORK TO THE BAÍA DE GUANABARA LNG TERMINAL NEW REGASIFICATION PROFILE

Philipe B. Krause Marcos Bruno B. Carnevale SIMDUT TRANSPETRO Rio de Janeiro, RJ, Brazil Rio de Janeiro, RJ, Brazil

Denis F. dos Santos Rodrigo B. L. Jardim TRANSPETRO TRANSPETRO Rio de Janeiro, RJ, Brazil Rio de Janeiro, RJ, Brazil

ABSTRACT important as a reference for future changes on operating supply Petrobras Transporte S.A. – TRANSPETRO’s Gas Pipeline units of TRANSPETRO gas pipeline system, showing the System, composed by 7.3 thousand kilometers, 135 delivery importance of pipeline simulation both as a planning tool for stations and 21 compressor stations, has a very seasonally pipeline logistic problems and as operational support. dependent operation. Highly linked with the Brazilian energy grid, during the dry season of the year a large part of the 77.3 million cubic meters of natural gas daily transportation are NOMENCLATURE used to generate around 6.4 gigawatts to power the country. TRBG Baía de Guanabara Regasification Terminal Additionally, the ever increasing number of power plants and LNG Liquefied Natural Gas distribution companies around the country demand more and GASENE Southeast-Northeast Gas Pipeline more gas to be offered to supply the system. Among the different ECOMP Compressor Station sources of natural gas available, the LNG is the most flexible UTE Thermal Power Plant for such seasonal operation. TECAB Cabiunas Terminal In order to support this current demand and to attend ONS National System Operator future demands, the regasification ability of Baía de MAOP Maximum Allowable Operational Pressure Guanabara LNG Terminal was increased in December 2012, by changing the regasification vessel that supplies the southeast portion of the gas pipeline network, from 14 to 20 million cubic INTRODUCTION meters per day. To prepare to receive the new ship, some tests Operating a complex gas pipeline network, with its many were performed to determine the operational limits on system intersections and mesh like configuration can be tricky, survival time without LNG supply during vessel exchange. This demanding a high level of attention to detail on the several assessment involved two different issues. The ship change segments concurrently, and being able to interpret and predict operation occurred during a period of high consumption, when the network response to different scenarios. Every intervention the LNG terminal was needed to sustain the network inventory. must be evaluated to determine the impact on the system, A long period without this supply, caused by the exchange of requiring continuous study in regards to the day to day LNG vessel, would affect the deliveries. On the other hand, the operation. new ship’s commissioning curve would introduce a large Transpetro operates Petrobras gas network, which includes amount of natural gas into the system during a short period of 7.3 thousand kilometers of pipeline, 21 Compressor Stations, time, demanding that the deliveries absorbed such volume. both owned and outsourced, 17 supplies and over 135 deliveries Four planning scenarios were assessed based on some expected across the country. The Figure 1 shows the network and its pipeline supply and delivery conditions. The work was geographic location within the country.

Figure 1. TRANSPETRO OPERATED GAS NETWORK

The Transpetro Gas Network can be divided in 3 separated On an existing system with complex delivery schedules, many systems. Each system has its own characteristics and factors must aligned effectively. peculiarities, from their physical configuration to the way they Specifically talking about a Regasification Terminal, the operate. The three regions are the North, the Northeast and the range of variables is enormous. From overhauling terminals and southeast network. While the North network is completely plants to ship scheduling and tide planning, the number of separated from the rest, both the Northeast and Southeast professional and discussion needed is overwhelming. This paper network are linked by a single pipeline system, called GASENE will focus solely on the view from the gas pipeline operation (Southeast-Northeast Gas Pipeline). view needs require to change the supply, and the experience The entry of a new supply or a significant change in an learned from it. existing one can drastically change the logistics of a pipeline network. They can affect contracts, change the gas quality of a delivery, change the flow direction or even decommission a PIPELINE NETWORK compressor station. Because of this, the possible effects of these To understand the Brazilian network as whole, one must changes in the system must be evaluated in great detail to first understand the country’s energy matrix. While most of the determine the full benefit. energy comes from hydroelectric power plants, this energy The more immediate side of this change, however, is when source is seasonal and highly influenced by changing climate. to introduce it to the network. From a new delivery, a new During the dry period, a number of gas thermal power plants are compressor station, or even a new supply, the effects on the used to save water at the reservoirs. Historically the dry period network can be easily controlled with adequate planning. When occurs between June and November. The Thermal plants are a changing an existing supply, however, it can be more complex. very important part the grid, especially during this period, so

2 Copyright © 2014 by ASME the safe and continuous operation of the gas network is to the other network represented here as deliveries, can also paramount to the country’s energy grid. function as supplies, depending on the network requirements. For the purpose of this study, the focus will be on the GASENE and Southeast network. The thermal plant locations operating at the time will pointed out on the network. The GASENE pipeline system is of the utmost importance to the operational safety of the network. Linking the Northeast and the Southeast network, it is composed by three supplies, two of which are in the top five supplies in the system, five compressor stations, a single power plant delivery and several small deliveries along the pipelines. A simplification of the network is presented in Figure 2. The northern limit is defined by the Catu compressor station, with a minimal operating pressure of 55 kgf/cm²g (53.94 barg), and responsible to supply a large part of the Northeast network. At the southern end, there is the Cabiunas Terminal (TECAB). While not in the figure, there is a compressor station inside the Terminal, as well as a natural gas processing unit. The TECAB is the link between the Southeast network and the GASENE system. All compressor station in this system can and do work bi-directionally during day to day Figure 2. GASENE NETWORK operation. This ability, added to the size of the pipelines, make the GASENE system the main storage element of the network. The Southeast network is the most complex network in the Located at the middle of both networks, with high volume whole country. With three different pipeline pressure limits, supplies and small deliveries, it’s responsible for most of the several supplies, compressor stations, refineries, thermal power networks operational flexibility. plants, large consumers and a connection with a different The compressor stations are Catu, Prado, Aracruz, Piúma pipeline network makes this pipeline grid difficult to operate and Cabiunas, located inside the TECAB terminal. The three and study. Figure 3 shows a simplification of the Southeast supplies are Cacimbas, UTGSUL and TECAB. The connections network.

Figure 3. SOUTHEAST NETWORK

As said before, the link with the GASENE system is made depending on the network condition. There are several thermal through the TECAB terminal. While represented here as a power plants, due specially to the fact the southeast is a high demand, the GASENE network can also work as a delivery, energy consumption area, where most of the country’s

3 Copyright © 2014 by ASME population and industry is located. Many refineries are also This was a significant condition during the operations planning, located in the region, contributing to the high delivery since there was a possibility of not having both ships (the old requirements. This high concentration of elements makes its one and the new one) present at the terminal. Exchanging ships operation very fast paced and dynamic, and in need of constant could require a minimum of 12 hours to complete. Any attention. problems during the maneuver, however, could extend that time to the next tide change. Considering that both ship were able to be simultaneously at the terminal, the time between the first ship REGASIFICATION TERMINAL AND SHIP leaving to the second actually mooring at the terminal was at The Baía de Guanabara Regasification Terminal (TRBG) least 9 hours, due to technical testing, pressurizing units, health was the second Brazilian regasification terminal built, alongside and customs agents checking the new ship and other the Pecém Regasification Terminal, located in the state of requirements. Ceará, in the Northeast network. Located in the state of Rio de The new ship had a flow testing curve required to insure its Janeiro, its right in the middle of the network high consumption operation. This curve, agreed previously with the ship company area. The original ship, operating since 2009, had the capacity had a top flow value of 24 million cubic meters per day and 72 to vaporize 14 million cubic meter of natural gas per day. A 28 hours length. Figure 4 shows the commissioning curve studied inch pipeline lateral between the main network and the terminal, originally. with 15.5 kilometers in length and with a MAOP of 100 kgf/cm²g (98.07 barg), completes the terminal transportation structure. The Baía de Guanabara is a very challenging area to maneuver ships and is highly dependent on tidal conditions.

Commissioning Flow Profile 25

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06:00 07:00 Gas Day 1 Gas Day 2 Gas Day 3 Gas Day 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 4647 48 49 5051 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 OPEN LOOP TRANSITION CLOSED LOOP

Figure 4. SHIP COMMISSIONING FLOW PROFILE

plant will operated, and at which capacity. Any changes on the GAS NETWORK CONDITION AND SCENARIOS gas power plant deliveries must first be approved by them. The expected dry season in Brazil, as stated before, is from The pipeline network was working on a weekly based June to mid-November. In 2012, however, the season extended profile. During the week days, the gas stored as usable line pack to January of the following year. This resulted directly in the was being consumed by the deliveries, especially the gas power continuous operation of the gas power plants, since the hydro plants, faster than the supplies could replenish it. The power plant reservoirs were at an all-time low level, well sustainability of the operation was insured by restoring the line beyond their safety point. As a consequence, all of the country’s pack on weekends, a period of lower energy and gas non hydro power plants were operating at full or almost full consumption. During the time period, The TRBG was working capacity. The National System Operator (ONS) controls the at almost full capacity during the week. It is an important asset country’s energy distribution system, determining which power to the operation, since it is one the few supplies with the ability to control the flow rate. Most of the others supplies come from

4 Copyright © 2014 by ASME associate gas wells, making it difficult to control flow without UTE MLG and UTE BLS are turned off during the operation. affecting the oil production. The LNG terminal allows for a fine All other deliveries maintain their original schedule. tuning of the supply/delivery ratio. 106 Scenario D. The average network pressure is 90 kgf/cm²g To study the problem, different scenarios were defined to (88,26 barg) at the high pressure pipelines and the power plants determine the maximum allowed time the Network could UTE MLG and UTE BLS are turned off during the operation. survive without the LNG terminal, considering also the All other deliveries maintain their original schedule. commissioning profile. To study these scenarios, three main control points were used to determine the constraints or boundary conditions for safe operation of the system during the MODELING simulation. These constraints were set considering the network The software use for these simulations was limitation and experience with the network operation: Catu PipelineStudio®, from ESI®. The base model used was compressor Station suction low pressure limit of 55 kgf/cm²g conceived by the operation programing and intervention area, (53.94 barg); the power plant UTE MLG delivery low pressure and is widely used in day to day operation. It has being limit of 60 kgf/cm²g(58.84 barg); and the Terminal high previously validated and tuned to insure optimum results with pressure limit of 100 kgf/cm²g (98.07 barg). the network. The main assumptions used in the modeling were:  Equation of State: BWRS Scenarios  Gas Equation: Colebrook The scenarios were determined after several compromises  Thermal calculation: Non Isothermal from all parties involved, including the ONS, to insure the  Minimum time step: 10 minutes smoothest transition possible, without affecting the delivery  Maximum time step: 30 minutes schedule of the network, whenever possible. The scenarios were  Knot spacing: Variable accordingly to pipe length based upon assuming the southeast network and the GASENE Due the size of the model used, some simplification are operated at a single average pressure on the high pressure made in regards to elevation profile and deliveries location, pipelines (with a MAOP of 100 kgf/cm²g or 98.07 barg) and all without affecting significantly the results. the power plants operating at maximum capacity. After this initial state, the TRBG supply initialize its ramp-down procedures to stop the terminal. The delivery schedule used was RESULTS based on a typical schedule for a week in December, but with Several simulations were attempted, using the software, to all the power plant operating. determine the maximum time the network could survive without The first two scenarios are based on the normal delivery the gas from the TRBG, keeping the original delivery schedule. schedule, with two different base pressure on the system. The The decision to turn on or off any compressor station was made purpose was to determine a range a time considering a lower to optimize this time, considering their availability during system pressure and a higher system pressure. The selected December 2012 (maintenance schedule, machine problems, pressure were chosen based on a review of historical data for etc.). the period. An interesting issue emerged from the initial results. While The latter two scenarios, while based on the same pressures the goal was to maximize the ship exchange time, it was noticed as the first ones, considered a different premise. The network that if the exchange time was too short, it wasn’t possible to operator can, due to maintenance or changes in the network immediately begin the commissioning profile without violating request a change in the delivery schedule of the network. For the MAOP of the pipeline lateral between the terminal and the the purpose of this intervention and through negotiations with main network. Too long time could affect deliveries and ONS, the delivery for two gas power plants would be turned off minimal pressure boundaries. These results showed that the only during the ship exchange, to insure the other deliveries and actual process had a fairly narrow window of opportunity, permit a longer ship exchange period, in case of any which helped reduce the number of simulations. contingency.

Scenario A Scenario A. The average network pressure is 80 kgf/cm²g Considering the high pressure pipelines at 80 kgf/cm²g (78.45 barg) at the high pressure pipelines and all deliveries (78.45 barg) average pressure and keeping the original delivery maintain their original schedule. schedule, it was found that the greatest allowable time for the Scenario B. The average network pressure is 90 kgf/cm²g ship change was 17 hours. Figure 5 shows the Terminal flow (88.26 barg) at the high pressure pipelines and all deliveries and pressure profile during the operation, to show the relation maintain their original schedule. between the commissioning profile and the terminal pressure, Scenario C. The average network pressure is 80 kgf/cm²g while Figure 6 shows the pressure profiles of the control points, (78.45 barg) at the high pressure pipelines and the power plants

Figure 7. TERMINAL FLOW AND PRESSURE (B)

Figure 5. TERMINAL FLOW AND PRESSURE (A)

Figure 8. CONTROL POINTS PRESSURE (B)

Figure 6. CONTROL POINTS PRESSURE (A) Scenario C Considering the high pressure pipelines at 80 kgf/cm²g (78.45 barg) average pressure and only interrupting the Scenario B deliveries of UTE MLG and UTE BLS during the ship change, Considering the high pressure pipelines at 90 kgf/cm²g the optimum allowed time for the ship change found was 35 (88.26 barg) average pressure and keeping the original delivery hours. Figure 9 shows the Terminal flow and pressure profile schedule, optimum time for the ship change was 34 hours. during the operation, to show the relation between the Figure 7 shows the Terminal flow and pressure profile during commissioning profile and the terminal pressure, while Figure the operation, to show the relation between the commissioning 10 shows the pressure profiles of the control points, to insure profile and the terminal pressure, while Figure 8 shows the that neither the maximum pressure at the terminal nor the pressure profiles of the control points, to insure that neither the minimum pressure at the deliveries was reached. maximum pressure at the terminal nor the minimum pressure at the deliveries was reached.

Figure 9. TERMINAL FLOW AND PRESSURE (C) Figure 11. TERMINAL FLOW AND PRESSURE (D)

Figure 10. CONTROL POINTS PRESSURE (C) Figure 12. CONTROL POINTS PRESSURE (D)

A summary of the results can be found at Table 1.The table Scenario D shows that while for scenarios A and B there is a small Considering the high pressure pipelines at 90 kgf/cm²g operational margin between the TRBG max pressure and the (88,26 barg) average pressure and only interrupting the UTE MLG and Catu minimum pressure, for scenarios C and D deliveries of UTE MLG and UTE BLS during the ship change, that margin is smaller, since both limits have almost been the optimum allowed time for the ship change found was 74 reached. hours. Figure 9 shows the Terminal flow and pressure profile during the operation, to show the relation between the Table 1. RESULT SUMMARY commissioning profile and the terminal pressure, while Figure 10 shows the pressure profiles of the control points, to insure TRBG UTE MLG Catu Ship Max Min Min that neither the maximum pressure at the terminal nor the Scenario minimum pressure at the deliveries was reached. Change Pressure Pressure Pressure (kgf/cm²g) (kgf/cm²g) (kgf/cm²g) A 17 h 96.83 60.41 55.52 B 34 h 95.11 60.10 57.38 C 35 h 99.65 61.73 55.62 D 74 h 99.59 61.82 56.37

CONCLUSION The objective of this paper is to show the importance of simulation and operational planning on pipelines. While this work was a small part of a larger project, it clearly showed that without a preliminary study of the gas network conditions, including knowledge of operational bottlenecks and the ability to simulate the network response, the ship change would have been much more difficult, and with a great deal of uncertainty on the ability to maintain delivery schedules. The expected use of compressor stations, the pressure fluctuation on the main supplies and deliveries were passed to the operators to assist in planning and executing the actual operation. The simulation showed that while the operational window was somewhat narrow, if the gas network operator could prepare the network prior to the ship change, while maintaining its delivery schedule, it would significantly improve the ability of the delivery schedules to be maintained in the event of unexpected delays in the LNG ship exchange and commissioning. During the actual operation, the network was at an even higher pressure than the ones simulated, at an overall 95 kgf/cm²g (93.16 barg), which require a verification using the same models used in the planning stage. This allowed a faster response from the contingency team in regards to delivery programming and operation follow up.